Recording artist Booker T. Jones shot to fame in the 1960s with "Green Onions," a bluesy instrumental that fused a bouncy Hammond organ and jangly Fender Telecaster into an instantly recognizable hit.

It's one of those songs - you might not know it by name, but you definitely know it.

"That track has been called iconic, groundbreaking, even classic," Mr. Jones told the House Judiciary Committee on Friday. "But some music services have a less-dignified name for it - 'Pre-72' - because of a quirk in the law."

Mr. Jones is one of many musicians who want Congress to close a loophole that allows satellite radio and internet streaming services to play hits from a bygone era without paying the artists who recorded them.

Decades ago, Congress extended copyright protections to tunes recorded after Feb. 15, 1972, yet never shielded older ones, leaving artists at the mercy of outdated state laws that may or may not compel payment.

Mr. Jones said he is lucky. He is still going strong, with recent gigs on both sides of the Atlantic. Yet the loophole is denying other artists the cash they need for growing medical bills or other expenses late in life.

Rather than enjoying hard-earned retirement, witnesses told Congress, recording artists are chasing down redress in the courts, forcing judges to decode a patchwork of statutes that were written long before Pandora Internet Radio ever set the mood for a dinner party.

"Artists are trying to protect their rights at the state level because of the lack of clarity at the federal level," Mr. Jones testified. "But time is running out for many of these legacy artists, and we shouldn't have to fight state by state to get the compensation we deserve."

Composers of pre-1972 songs have protection, but recording artists do not. Sometimes the composer and performer are the same person, though sometimes they aren't.

Actress and singer Dionne Warwick said it's crazy that she gets paid for singing "I'll Never Love This Way Again," from 1979 but not "I'll Never Fall in Love Again" from 1969. She didn't write the songs, but she did make them popular.

"I don't think it's fair," Miss Warwick testified.

Rep. Darrell E. Issa, California Republican, and Rep. Jerrold Nadler, New York Democrat, are pushing a bill - the Classics Act - that would create parity for pre-1972 works so digital platforms pay for them in the same way they do for more recent recordings. Namely, royalty amounts would be established by an outside entity and then be distributed to performers and record labels.

Sponsors say the legislation would be a win-win for artists, who would receive consistent pay, and streaming services, which would no longer contend with uneven rules and costly litigation.

The legislation is part of broader efforts by members of Congress to update copyright laws and help musicians in the rapidly evolving digital age.

A spreadsheet known as the SoundExchange keeps tabs of what is played on internet radio and pays artists accordingly, though artists told Congress that those "micropenny" payments are inadequate.

"For songwriters, it is not uncommon for millions of streams to equal only hundreds of dollars in royalty payments," Tom Douglas, a songwriter from Nashville, Tennessee, told the judiciary panel at Friday's field hearing in New York City.

Yet artists who recorded songs prior to 1972 might get nothing at all.

Songs played through internet services are considered a type of public performance rather than a downloaded copy of a work, and courts have struggled to determine whether copyright protections in states such as California, Florida and New York extend to digital streams.

Lawsuits against services such as Sirius XM radio and Pandora have resulted in mixed rulings and costly settlements, prompting cries for federal reform.

SoundExchange, Pandora and the Recording Industry Association of America released a statement last year in support of the Classics Act. Sirius XM did not return an emailed request for comment on the proposal.

It's unclear how Congress let the problem get to this point.

Even the U.S. Copyright Office says it is confusing, writing in a 2011 report: "Congress did not articulate grounds for leaving pre-1972 sound recordings outside the federal scheme and there is very little information as to why it did so."